I wasn't terribly impressed by the first couple of Beowulf trailers. But now, having seen the entire thing, in 3D, consider me mightily impressed. Beowulf is an amazing visual feast and a startling display of what's possible with motion capture and CG effects. Director Robert Zemeckis sure loves his technology, and while I'd like to see him make something akin to Used Cars again, he's a far better filmmaker than his friend and USC contemporary George Lucas, and so Beowulf has more thrills, more emotion, and more decent acting than all three Star Wars prequels combined.
The "humans" still have that dead eye look if I'm really honest, but this is a big step on from what Zemeckis achieved with Polar Express. And while almost all the cast's digital creations look more or less like themselves (save Ray Winstone's buffed Beowulf and Crispin Glover's hideous Grendel) the one character who looks truly alive digitally is Angelina Jolie, but that may be, in the flesh, she looks beyond "real". (What I'm trying to say here is that some actors, look different to mere mortals, and she's one of them.)
Anyway, back to the film itself. The 3D is sensational. And having suffered through several 3D films during the 80s revival, I can safely report that the dimensional work is the best I've encountered and after two hours I emerged from the cinema without feeling as if someone had stuck a hot needle in my eye, as I have in the past.
In short, go and see this film. Monster House may, scene for scene, be more inventive, but Beowulf is arguably more spectacular.